1. Field of the Invention
The present invention relates to a device for the optoelectronic detection of switching positions of a mechanically actuated, positively driven switching element that engages in a detent curve in which the device has an optical transmitter positioned to illuminate an optical receiver, and the device further has a shutter which is displaceable relative to the transmitter and the receiver and displaces in response to movement of the switching element between switching positions.
2. Background Art
Devices for the detection of switching positions are used in switches with which a plurality of functions can be switched, and in which the mechanical haptics and electrical switching position detection device are separated. Switches like these are used as lighting or steering column switches in motor vehicles, for example. Such switches are designed to be displaceable in a plurality of directions, so that the numerous functions can be performed independently from each other and parallel to each other. A switching position detection device makes the respective switching position directly accessible to the switched devices, or even as a data input of a data processing system, e.g., an onboard computer in a motor vehicle, for monitoring and control purposes.
In addition, back-lighted symbols can be allocated to the switch for displaying the respective switching position. In this case, the symbols standing for the actually switched functions are back-lighted as a function of the respective switching position.
Such switches are conventionally designed as contact switches, so that a switching position is reached once the switching component has established the corresponding electrical connection. Even though numerous different functions can be switched with such a multifunction switch, the effort increases disproportionately for complicated switch structures if the object is to detect the respective switching positions in the manner described above. In addition, the elements provided for mechanical contacting are subjected to wear and ageing.
As known from DE 43 32 748 A1, multifunction switches can be designed as contact-less, optoelectronically operating switches. The switch described in this document is characterized in an electrical contact is not established to detect a switching position. Rather, a photosensitive element is exposed to light as the receiver with the switching element in a specific switching position. In addition to the photosensitive element, such an optical switch encompasses a light source, e.g., which can be arranged on the same printed circuit board as the photosensitive element.
An optical fiber whose area on the light decoupling side faces the photosensitive surface of the photoelectric element conveys the required light to the photoelectric element. A movement gap is between the decoupling side of the optical fiber and the photoelectric element. A shutter is in the movement gap. The shutter is coupled to the coupled to the displacement of the switching element and moves in the movement gap as the switching element moves between switching positions. The shutter has an opening at a predetermined position, so that, after the switching element has been displaced to a specific switching position, the opening is aligned with the area of the optical fiber on the decoupling side and the photosensitive surface of the photoelectric element, so that the photoelectric element can be exposed to light.
If the switching element is displaced from this position again, the photoelectric element is shaded, and the device moves out of the switching position. Therefore, each switching position is realized by the object of this document by means of an optoelectronic switch. Suitably arranging a plurality of such optical switches also makes it possible to detect complicated switching displacements. However, it is difficult to realize complicated switching displacements in the manner described given tight mounting spaces.
In conceiving this known device, it is necessary that the transmitter and the receiver be precisely aligned relative to each other, in particular when a distinction is to be made as intended between even small make-and-break cycles. Due to the resultant tolerance chains during the manufacture and positioning of photoelectric barrier and the shutter, it can happen that an optical receiver in a specific switching position is not sufficiently irradiated by an optical transmitter after the elements have been installed, e.g., in the housing of a steering column switch, to determine its switching positions, so that there might not be enough illumination intensity for detecting this switching position under certain conditions.